installing fan in smoker

kiyotei · August 30, 2007, 10:52:26 AM

I sent out a couple of private messages but not sure how often people check their email on here, so I am going to also start this thread.

I was reading the link about installing a fan in the smoker. I noticed no one tried to install the fan below the V shaped drip pan. I would think it that under the drip pan would be the best location. This would require that the motor be mounted on the side of the smoker vs the back. Is it that everyone just wants the fan on the back of the smoker? Mounting under the drip pan also makes use of the vents to more evenly distribute the heat and not blow the heat on the lowest rack. I just got my fan from Grainger and will be installing it before the weekend. Then I plan on smoking some brisket and pork butts.

Mr Walleye · August 30, 2007, 11:02:42 AM

I do recall there being a discussion on mounting it there before but I can't remember the result. Ill have to see if I can find it. I mounted mine in the usual spot at the back between the V-pan and the lowest rack.

Mike

Mr Walleye · August 30, 2007, 11:13:06 AM

Here is 1 small discussion on it.

http://forum.bradleysmoker.com/index.php?topic=4636.0

Mike

kiyotei · August 30, 2007, 02:12:18 PM

thanks for the link. I'll ask the one guy how it worked out for him installing it below the drip pan.

kiyotei · September 02, 2007, 08:53:24 PM

I successfully installed the fan. I will take some pics and explain what I did soon, so stay tuned.

kiyotei · September 03, 2007, 05:45:44 PM

Installing a air circulation fan

1 Motor: Grainger Item # 4M079
2 Fan blades Grainger Item # 2C948 (though I suggest trying the 2.5" model 2C949 if it will fit)
1 Electrical junction box
6 #8-32 1 ¼" long bolts, washers, nuts (to mount the junction box)
2 L brackets (attach junction box to smoker)
3 wire nuts (used to join wires, +, -, and ground wire)
6 #8-32 ½" long bolts, nuts, washers (to attach L brackets to utility box).
2 #8-32 21/2" (verify this is the correct length for you stuff) bolts, nuts, washer (to mount motor to junction box).
1 long metal bracket (to help mount motor to junction box)
1 8ft outdoor extension cord (3 prong)
1 strain relief for wires
1 wire prong for attaching ground wire to motor
1 insulated wire terminal (ground wire)
Tie wraps for securing wires

The goal is to circulate the air just enough to get even heating through out the smoker. I have found using a digital thermometer that my OBS has a very large temperature variation from bottom to top. Below the bottom shelf in the back I read around 300 degrees after an hour plus (empty smoker). The door thermometer reads about 250 degrees. I verified this with my digital thermometer.

After installing the fan and doing some testing, I'm not sold on the 2" fan blade being able to move enough air in the smoker. I placed all 4 racks in the smoker with a piece of foil on each rack to simulate meat (for air flow not temp absorbing). I did not see a big improvement using the fan. I will play some more. I think I would prefer a slightly larger fan blade. However this could be a problematic since the location I chose will most likely only have room for a 2" fan blade. It's possible the 2.5" fan would fit but it I would have to buy one and try it to verify this. I may search for another 2" fan blade that moves more air. This model is rated at 35 CFM. I think the 2.5" fan is rated around 45 CFM. I think PC fans are around 300 CFM.

Before drilling make sure you remove the back right side of the smoker to locate where all the wires are. There is a temperature sensor about ½ way up the back wall. It's wired to the thermostat and heating element.

I had to remove the two 2" mounting bolts that came with the motor and replaced them with 3" 8-32 bolts. These are a too long but I didn't feel like removing them and going with a shorter bolt. I had to drill two holes in the back of the junction box to mount the motor. Of course there were already two holes there which were almost perfectly located, almost. This screwed up things for me because when I drilled the holes, the bit ate into the existing holes! So I had to add a long metal bracket to the back of the junction box to help support the motor. You can see this in the pics (not pretty but I don't have great tools to work with). I also tie wrapped the wires to the junction box to keep them from flopping into the fan. Using 3 wire nuts, I wired the motor to an 8ft extension cord which I cut the end off. I wired the ground plug from the extension cord to one of the motor mounting bolts. The 2" fan blade fits between the bottom rack and the drip pan. I mounted the fan here following the lead of others. I have no idea if this is the best location. I have the fan blowing towards the door. I almost never use the bottom rack so I'm not worried about the fan drying out the meat on the bottom rack. Anyhow, I located the position for the motor shaft and drilled a hole from the inside of the smoker to the outside. I inserted the motor and hand spun the shaft making sure that it was not rubbing against the walls. I then wrapped some masking tape around the motor shaft and slide it through the hole. The tape makes sure I have a little room for error around the shaft. You don't want the shaft rubbing against the smoker walls. I laid the smoker on its front (supported on some bricks to make sure the temperature slide at the base does not get damaged or bent!). I reinserted the motor into the hole and drilled the holes for the mounting bracket. You should use at least two bolts per L bracket. I had to drill extra holes in my L brackets. I found that sheet metal screws did not do the job and had to drill all the way through the smoker and mount with nuts on the inside wall of the smoker. FYI it's very easy to drill through the smoker walls. I then removed the motor, took the masking tape off of the shaft and reinserted the motor. I inserted the bolts (1 ½") and stood the smoker up. I then added the washers and nuts to the bolts. I turned the shaft again to make sure it was not rubbing. I plugged it in and it ran ok, no strange noises. I then took the fan blade and a pen and marked the location of the bolt used to secure the blade to the shaft. I did this because once you stick the fan blade on the shaft you cannot see where the bolt is. One final note, in the pics of the inside of the smoker, you may noticed a couple of extra bolts (really big washers) there are holes from my first attempt. I had to redo it because the first junction box I bought did not work.

Mr Walleye · September 03, 2007, 06:10:32 PM

I also installed a fan very similar to your installation. One difference is I ran the "L" brackets from the box right to the edge of the tower. this seems to provide a little more support. The other thing I did was I reversed the motor. I think if you do some reserch most have done it this way. By doing this the fan blade goes on the shaft the opposite way, this makes it a whole lot easier to tighten it onto the shaft.

Another thing you could do is slightly change the pitch of the fan blade which may effect the cfm.

Mike

kiyotei · September 03, 2007, 06:53:35 PM

I could not find a junction box that was deep enough to fit the motor and external fan in completely. I needed to slide the L brackets out a bit to give the fan enough clearance from the back of the smoker. I also could not find a junction box with L brackets already attached. I read the bit about reversing the fan. The logic was that this would prevent the fan from drying meat on the bottom rack. I don't use my bottom rack so I didn't see the need to do that. Thanks for the info though.

Habanero Smoker · September 04, 2007, 03:21:55 AM

Thanks for the write up, and the detailed parts list. I order my motor and blades last Friday, but haven't gotten an order comfirmation yet.

kiyotei · September 04, 2007, 08:01:02 AM

I think the hardest part was keeping the fan shaft centered in the hole while I drilled the mounting holes for the junction box. That's why I recommend wrapping the shaft in tape to give ya some room for error.

Habanero Smoker · September 04, 2007, 02:16:35 PM

I see you decided to install above the V-Tray. Any particular reason why you finally decided to go in that direction?

kiyotei · September 04, 2007, 02:39:35 PM

I decided to be a follower not a leader. I think it was the right choice with the fan I installed. Its CFM of 35 is way too low to help move air up from under the drip pan. If you go under the drip pan, I think a CFM of a 100 would work much better. I figure if you install the fan on the side of the smoker opposite of the wood burner, you can use the water bowl to divert the airflow away from the wood so it does not burn too fast.

Habanero Smoker · September 05, 2007, 01:49:03 PM

I believe you made the correct choice.

I just recieved my fan motor and blades this afternoon. Now it's just a matter of getting the other parts, and finding time to install it. I'm hoping I can do it by Saturday, before my next smoking projects, but that's not looking too realistic.

kiyotei · September 05, 2007, 03:26:18 PM

Based on the intial results I got smoking on Saturday, I would recommend, if possible, mounting the fan such that you have the option of using the 2.5" fan in the future. I'm not sure there is enough clearance if you always use your bottom shelf. If you never, ever use your bottom shelf, you could shift the hole for the shaft up slightly higher than what I did. I actually ordered the 2.5" fan and it arrived today. I'm gonna play with it and see if it works better. I may have to bend my drip pan to get the clearance it needs. I definetly won't be able to use the bottom shelf with out a little bending there too. I never use my bottom shelf so not a big deal really. Currently I just have a cast iron bread pan sitting on it to act as a heat sink to heat to improve the temp rebounding after opening the door. I normally use just 2 shelves max so I can always move my cast iron plate up one shelf.

winemakers · September 06, 2007, 07:08:12 AM

Prior to my fan installation, I had a peck full of doubts about the 'above the V pan' and low cfm of the arrangement. However, post installation (below the vpan, low cfm fan/motor combo), I have had good results. My thought process went to gently mixing the air, inline with the low and slow heat/time process, rather than a much higher flow rate that would mix in a far more complete, albeit, turbulant manner.

So far, success, with plus/minus 2 degrees from top to bottom rack and none of the dreaded 'jerky effect' on the bottom rack meats during my high capacity smokes. I have been pleased.

Unfortunately, my pid pooped the sheets last weekend, >:(. I believe I will fire up a Love controller TS, installed in the lower panel, as stickbowcrafter did. That was/is a very slick application.

mld